開く
【あく】
to open (e.g. doors), to open (e.g. business, etc.), to be empty, to be vacant, to be available, to be free, to be open (e.g. neckline, etc.), to have been opened (of one's eyes, mouth, etc.), to come to an end, to open (one's eyes, mouth, etc.), to have a hole, to form a gap, to have an interval (between events)

開ける
【あける】
to open (a door, etc.), to unwrap (e.g. parcel, package), to unlock, to open (for business, etc.), to empty, to remove, to make space, to make room, to move out, to clear out, to be away from (e.g. one's house), to leave (temporarily), to dawn, to grow light, to end (of a period, season), to begin (of the New Year), to leave (one's schedule) open, to make time (for), to make (a hole), to open up (a hole)

空
【から】
emptiness, vacuum, blank

空っぽ
【からっぽ】
empty, vacant, hollow

もぬけの殻
【もぬけのから】
completely empty, vacant, deserted, (everything) gone

空く
【すく】
to become less crowded, to thin out, to get empty, to be hungry